1. Field of the Invention
The present invention relates generally to buffers used in semiconductor circuits, and more specifically to a source/emitter follower buffer that drives a switching load, and has improved linearity.
2. Related Art
Buffers are often used in a semiconductor device to isolate one portion of the device from another portion, generally to minimize the characteristics of one portion from influencing the operation of the other portion. A buffer generally contains at least one transistor and the buffer is termed as a source follower when the output is provided from a source terminal and as an emitter follower when the output is provided from an emitter terminal. In both cases, the input signal is provided to the control (gate or base) terminal of the transistor.
Buffers often drive switching loads. A switching load generally refers to a load which is electrically connected and disconnected from (a source of) a signal in different intervals of time. Examples of switching loads include switched-capacitor components such as switched-capacitor analog to digital converters (ADC), switched capacitor filters, etc. In a common configuration associated with switching loads, a buffer receives the input signal, and provides a corresponding output signal to the switching load.
It is generally desirable that an output signal of a buffer have as linear a relation as possible with an input signal, i.e., the buffer operate with a high degree of linearity to ensure that the output signal is a correct representation of the input signal.